In order to operate normally, most modern electronic devices require a constant voltage supply. Digital DC-DC converters are generally used to supply constant DC voltage to circuits such as Very Large Scale Integrated (VLSI) circuits or system-on-chip circuits.
Digital DC-DC converters convert an analog voltage output through an output terminal to a digital output voltage, and then compare the digital output voltage with a preset reference voltage to adjust the output voltage to a desired level. To accomplish this, digital DC-DC converters typically use a Pulse Width Modulation (PWM) controller as shown in FIG. 1.
FIG. 1 is a block diagram of a conventional digital DC-DC converter.
The conventional digital DC-DC converter shown in FIG. 1 is a PWM digital DC-DC converter, which includes a power switch 110, a rectifier 120, an A/D converter 130, a duty up/down determinator 140, and a PWM duty controller 150. The switch 110 switches on/off an input voltage Vin according to an input switching signal, and the rectifier 120 rectifies a voltage output from the power switch 110. The A/D converter 130 converts an analog output voltage Vout of the rectifier 120 to a digital signal, and the duty up/down determinator 140 determines duty up/down based on the digital signal from the A/D converter 130. The PWM duty controller 150 controls switching of the power switch 110 for duty control based on the duty up/down determination signal from the duty up/down determinator 140.
The conventional DC-DC converter typically employs a digital scheme using a flash A/D converter, and adjusts the output voltage Vout by comparing it with a reference voltage.
Since the output voltage Vout of the DC-DC converter is analog, the DC-DC converter uses the A/D converter 130 for interfacing with the digital components such as the up/down determinator 140 and the PWM duty controller 150. A flash A/D converter is typically used as the A/D converter 130.